Manufacture of explosives, celluloid, or the like.



110,723,311. 1 PATENTHD MAR. 24, 1903. R. ROBERTSON & W. RINTOUL.

MANUFACTURE OF EXPLOSIVES, CELLULOID, OR THE LIKE.

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1 MANUFACTURE OF 'EXPLOSIVES, GELLULOID,OR THE LIKE. AP PLIOATION FILED 001'. 10, 1902. N0 MODEL;

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UNITED STATES,

;PATENT OFFICE.

ROBERT ROBERTSONAND WILLIAM RINTOUL, OFWALTHAM ABBEY,

ENGLAND.

MANUFACTURE OF EXPLOSIVES, CELLUILOID, OR .THE LIKE.

SPECIFICATION forming part of Letters Patent N 0. 723,311, dated March 24, 1903. Application filed October 10, 1902; $erial Ne. 126,795. (No specimens.)

To aZZ whom it may concern:

. Be it known that we, ROBERT ROBERTSON, analytical chemist, and WILLIAM RINToUL, analytical chemist, subjects of the King of Great Britain and Ireland,residing at Oxford Villas, Wal tham Abbey, in the county of Es-f sex, England, have invented certain new and useful ImprovementsRelating to the Mann-j facture of Explosives, Celluloid, or the Like, (for which we have made application in Great Britain for Letters Patent, Nos. 25,993/01 and 25,994/01, hearing date the 19th of December, 1901,) of which the following is a specification.

Our invention relates to the recovery of acetone used as a solventin the manufacture of explosives, celluloid, and the like. For ex: ample, in the manufacture of cordite when the kneading has been completed and the cord pressed the corditeretains a large proportion of the solvent, which is then driven oif in drying houses or stoves and is usually lost. Again, in the manufacture of waterproof fabrics or materials, which are made by impregnating or coating a sheet of suitable material with a nitrocellulose, the best solvent known is acetone; but. this owing to its cost could not be commercially employed, as no practicable method of recovering the acetone used in such amanufacture existed.

The object of "our invention is to recover the acetone which is used insuch manufactures and which exists in drying stoves or inclosures in a state of comparatively great at tenuation mixed with air.

Now it is well known that acetone combines withbisulfites-such as bisulfite of sodium, potassium, magnesium, calcium, (kc-when the acetone is mixed with solutions of the salts. Considerable difficulties, however, occur in the application of this reaction to the practical recovery of acetone as employed commercially in the manufacture of explosives and the like owing to the comparatively great state of attenuation of the acetone-vapor in the Our-invention is based on the fact which we have discovered that such solutions of hisulfites are capable under suitable conditions, for example, by means of a gas-scrubbingprocessof extracting a large proportion of the acetone -vapor from a mixture with air even though the vapor be only pres ent in a state of great attenuation.

Our invention therefore consists in a process for the recovery of acetone existing as vapor in mixture with air by causing the mixture to come thoroughly into contact with solutions'of bisulfi tes, such as bisulfite of sodium or potassium, and subsequently distilling the bisulfite compound either directly, with subsequent rectification in the presence of. an alkali, or by the addition of an alkali and subsequent distillation.

Our invention further consists in a method of removing the greater part of the sulfate from the bisulfite solution containing acetone by cooling the latter. l

- Our invention also consists in applying our acetone-recovery process to the manufacture of materials or articles in which a dissolved nitrocellulose or its equivalent is employed.

Referring to the accompanying drawings, Figure l is an elevation, and Fig. 2 is a plan, of one general arrangement of apparatus suitable for the carrying out of our process. Fig. 3 is a sectional elevation, and Fig. 4 a plan, of, a scrubbing-tower suitable for use in our process, while Fig. 5 is an end view, and Fig. 6 a plan, toan enlarged scale, showing details of the double trough.

According to one modificationthe air mixed with acetone is led from the drying house or inclosure through a pipe I) to the bottom of a scrubbing-tower c, from the top of which it is led through another pipe 5 to the bot tom of the next tower c and so on through as many more towers as are necessary to carry out the process. The air may be drawn through the towers by any suitable form of aspirator or ejector cl. The solution of bisulfite of soda is stored in a tank 6', which may be conveniently supported on the wall of the drying stove. From this tank it passes through a pipe f to the top, preferably, of the tower from which the air finally issues, and after passing through this tower and coming into intimate contact with the mixture of air and acetone to be treated passes away from the bottom of the tower to a vessel It, constructed on the model of an ordinary Wolifs bottle or monte-j us. Compressed air may be used to force the liquid back from this vessel through the pipe 71 to a second tank a the cycle being repeated through the other towers. The solution which is finally drawn off is then treated for the recovery of the acetone, as is described below.

Similar parts areindicated in the drawings by the same letter with a different numeral suffix.

For the purpose of bringing the bisulfite-ofsoda solution thoroughly into contact with the mixture of air and acetone to be treated we prefer to employ towers having a large number of parallel strands, ropes, tapes, threads, or the like on which the liquid is carried, these threads being preferably arrau ged with interlacing fibers relatively close together and so that they present an exceedingly large surface for cou tact with the mixture of acetone and air which is passed through a chamber containing them. These threads offer comparatively small resistance to th flow of the gas through them, and thus enable uniform distribution and a very thorough contact between the liquid and the gas to be secured with an apparatus of comparatively small bulk. These towers, shown in detail in Figs. 3, 4, 5, and 6, consist of a tall oblong shell on of suitable material provided with a lid 02, through which pass pipes 0 r for drawing off the gases and supplying the absorbent liquid, respectively. The tower isclosed at the bottom with the exception of an inlet-pipe s for the gases and another pipe 25 for running off the absorbent liquid. The tower is preferably divided by partitions into several divisions or cells, branches 7" r r r from the main pipe supplying the absorbent liquid being led along the top of each cell. Immediately under each supply-pipe is a dish or trough preferably constructed of an inner portion 1/. and an outer one '0, so arranged one Within the other that the strands or threads which pass between them pass through the absorbent liquid which has trickled over from the inner trough u, the edges of which are suitably lipped. The strands may be allowed to hang vertically inside the tower; but the arrangement we prefer is as follows: A framework adapted to fit into each division or cell of the tower is built up of cross-bars w 10, passing between two end plates 0: m, the topmost bars being adapted to support the troughs u 1), while the strands are threaded between the other bars in the manner explained below. The contents of each cell of the tower constructed according to this arrangement can thus conveniently be lifted out as a whole when necessary for overhauling or examination. The partitions separating the frames may be dispensed with, the fibers in adjacent frames being brought almost into contact with each other. The strands are preferably arranged as follows: After passing over the side of the lower trough 'u the strands are carried downward at an angle of about seventy-five degrees to the side of the tower parallel to each other and at such a distance apart that the small fibers in adjacent strands somewhat interlace. They now pass over one of the bars to and are then carried downward atan angle to their former course until they reach the opposite side of the tower, where they pass around another bar to, and thus zigzag from side to side to the bottom of the tower, each layer making an angle of about thirty, degrees to the preceding one. As the parallel strands extend from side to side of the tower or section, aseries of screens isthus formed, through which the gases to be treated are made to pass. A second set of strands starting from the opposite side of the trough may be arranged in such a manner as to interlace with the first set, as shown in Fig. 3, and in this way an increased efficiency is obtained with the same tower-space. The angle of inclination of the fibers may be varied according to the nature of the absorbent and q the desired rate of flow; A suitable baffle a is provided for the more uniform distribution of the gases through the tower and to prevent the liquid from getting into the gas-inlet pipe 8. The method of using the tower is to allow an absorbent solution to flow down the strands, and this solution being distributed in its course over a multitude of interlacing fibers presents a very large surface of active liquid to the ascending gas driven or aspirated through the apparatus without causing any appreciable heading back of the gas-current. The solution we prefer to employ consists of thirty parts, by weight, of sodium bisulfite in a hundred parts, by volume, of solution. This strength of solution is not essential, though we find it very suitable; but if weaker solutions be employed a larger volume of liquid has to be handled. In order to prevent undue evaporation of the bisulfite liquor, we prefer to saturate the air with moisture before treatment either by means of a tower through which water is passed or by other suitable means.

For the recovery of the acetone from the bisulfite solution after it has passed through the towers the liquid is passed into a still it, connected to a condenser Z. This part of our process may be efiected in several ways. For instance, the solution containing thebisulfite compound may be distilled with sufficient alkali to form sulfite and the acetone con- .densed and rectified in the usual manner, or

it may be treated by the following process, which we have found specially suitable. We have found that on direct distillation without the addition of any alkali practically all the acetone has distilled over before any substantial quantity of the bisulfite present has become decomposed, and the small amount of sulfurous acid which is driven over can be recovered as sulfite by the addition of an equivalent quantity of alkali to the primary distillate before final rectification of the acetone. This method has the great advantage that it does not involve the conversion of the bisul- ICO IIO

fite into. sulfite, and the greater part of the bisulfite solution is available again for absorption, preferably after treatment with a relatively small quantity of sulfurous acid.

During the time the bisulfite solution is exposed to the oxidizing action of the air a certain-amount of oxidation to sulfate takes place. cumnlate, it might interfere with the action If this sulfate were allowed to acof the absorbent. We find, however, that the sulfate formed is only, slightly soluble at moderately-low temperatures in a solution of bisulfite containing a small quantity of acetone. If, therefore, after being sufficiently saturated with acetone-vapor in the tower the solution is cooled down somewhat, the excess of sulfate crystallizes out, leaving the solution sufficiently free from sulfate for further use in the towers after the acetone has been distilled off.

It will be obvious that the mixture of acetone-vapor and air might be made to come into contact with the gas by means of ordinary scrubbing-towers or by bubbling the air through a series of vessels containing a bisulfite solution without departing from our ining the mixture into intimate contact with a solution of a bisulfite and subsequently separating the acetone.

2. The process for the recovery of acetone from admixture with air, consisting in bringing the mixture into intimate contact with a solution of a bisulfite and subsequently separating the acetone by distilling the compound directly, practically all the acetone coming over before any substantial decomposition of the bisulfite has taken place and recovering the small. amount of sulfurous acid which does come over by the addition of an alkali, before final rectification of the acetone.

3. The process for the recovery of acetone from admixture with air, consisting in bringing the mixture into intimate contact with a solution of a bisulfite subsequently recovering the acetone and separating any sulfate that may form by cooling the liquor, the sulfate being only sparingly soluble at comparatively low temperatures and therefore crystallizing out.

4. The process for the recovery of acetone from admixture with air consisting in saturating with moisture the mixture to be treated and bringing it into intimate contact with a solution of bisulfite and subsequently separating the acetone.

In witness whereof we have hereunto set our hands in presence of two witnesses.

ROBERT ROBERTSON. WILLIAM RINTOUL.

Witnesses to the signature of the said Robert Robertson:

JOHN ALEXR. ROBERTSON, ROBERT ROBERTSON. Witnesses to the signature of the said William Rintoul:

MATTHEW ATKINSON ADAM, GEORGE ISAAC BRIDGES. 

